The present invention relates to displays and, more particularly to an illuminated display comprising, an elongated cold cathode gas discharge tube containing an ionizable gas, the tube having a single cathode element at one end in contact with the gas; and, a power source connected to ionize the gas and cause illumination thereof, the power source being connected to the single cathode element and producing alternating voltage referenced to ground potential and of sufficient frequency to cause the gas to ionize through the natural surrounding capacitance between the ionized gas and ground potential.
Cold cathode gas discharge displays are old and well known in the art. The most familiar is the "neon sign" 10 of FIG. 1, which has remained virtually unchanged from time immemorial. In neon sign 10, an elongated glass tube 12 is filled with an ionizable gas 14, such as neon. The tube 12 has a pair of cathode elements 16 passing through the glass at the ends of the tube 12 into contact with the gas 14. The secondary of a high voltage, current limited transformer 18 is connected across the cathode elements 16. The primary of the transformer 18 is connected via plug 20 to a standard 110 volt, 60 Hz wall socket, or the like, which results in a 60 Hz, high voltage being applied across the gas 14 by the cathode elements 16. The high voltage causes the gas 14 to ionize and glow, thus causing the desired illumination. Particularly as the signs get older, the use of high voltage causes buzzing, and the like, which is annoying and disruptive.
Neon signs such as 10 are typically used in two ways. They can be disposed behind a display panel having indicia thereon (not shown) and used to illuminate the panel. More commonly, the tubes 12 are formed into the letters, or the like, to convey the desired message. In either case, however, the entire length of the tube 12 must be energized simultaneously. For "movement" of the display, individual tubes comprising the various segments must be employed with each connected to an individual source of power. Moreover, timing and power control circuits must typically be utilized in this approach.
Wherefore, it is the object of the present invention to provide a new approach to the manner of operation of gas discharge tubes which provides for ionization of the gas with a single cathode element.
It is another object of the present invention to provide a new approach to the manner of operation of gas discharge tubes which provides for low voltage operation thereof.
It is yet another object of the present invention to provide a new approach to the manner of operation of gas discharge tubes which provides for selective ionization and illumination of portions of the tube.
It is still another object of the present invention to provide a new approach to the manner of operation of gas discharge tubes which provides for moving illumination of the tube in an illuminated handwriting style.
Other objects and benefits of the present invention will become apparent from the description contained hereinafter in combination with the illustrative drawing figures.